romegalic patients have continued to be followed with respect to pituitary radiation. Further, we are evaluating the effects of transphenoidal pophysectomy in these patients and comparing them to the tuitary-irradiated patients. cently, human growth hormone has been cross-linked to its specific cellular ceptor on IM-9 cultured lymphocytes. Under reducing conditions the edominant band is an approximate 140K protein. Under non-reducing nditions, however, a molecular weight component of approximately 270K is served. Further attempts were made to see if the growth hormone receptor s a protein kinase or a substrate for this kinase activity; it is not. us, the growth hormone receptor is not analogous to the insulin receptor. e heterogeneity of circulating growth hormone in plasma has been studied. tuitary growth hormone was injected in normal volunteers and the individual owth hormone components isolated by gel filtration. It was found that the lf-time of the "little" (22,000 Dalton) growth hormone component was faster an the "big" and the "pre-big" growth hormone components, respectively. is is compatible with a receptor-mediated type of removal of these mponents; previous studies have shown that the high molecular weight forms ve lower radioreceptor activity than the 22,000 Dalton growth hormone eparation.